Name: lipid anchors in membrane proteins
Uploaded: 2023-04-30T09:16:02.000Z
Duration: 1 min 32 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.B.1.4.a

Lipids as Anchors

가장 일반적인 세 가지 유형의 지질 앵커는 프레닐기, 지방 아실기, 글리코실포스파티딜이노시톨 또는 GPI 앵커입니다.
프레닐기는 15개의 탄소 파르네실기와 20개의 탄소 게라닐게라닐기입니다. 그들은 단백질의 카르복시 말단 또는 그 근처에서 시스테인 잔기에 결합합니다. 
포화 14 탄소 미리스트 산과 16 탄소 팔미트산은 단백질에 연결된 가장 일반적인 지방 아실 앵커입니다.
미리스틱산(myristic acid)의 첨가 또는 미리스토일화(myristoylation)는 단백질의 N-말단 글리신 잔류물에서 발생합니다. 단백질의 팔미토일화(Palmitoylation)는 N- 또는 C- 말단 시스테인 잔기(cysteine residue)에서 발생할 수 있습니다.
프레닐화(Prenylated), 미리스토일화(myristoylated) 및 팔미토일화(palmitoylated) 단백질은 세포 내 신호 전달 경로와 단백질-단백질 상호 작용에서 필수적인 역할을 합니다.
GPI 앵커는 세포외 단백질에 부착되며 포스파티딜이노시톨, 글루코사민, 3가지 만노스 및 포스포에탄올아민의 핵심 구조를 포함합니다.
포스포에탄올아민은 표적 단백질의 C 말단 아미노산에 결합하고 인지질은 막의 바깥층에 삽입됩니다.
이를 통해 GPI 고정 단백질은 세포-세포 통신 및 세포 접착과 같은 세포 외 기능에 참여할 수 있습니다.

앵커로서의 지질

원형질막에서 이중층을 형성하는 지질은 단백질을 막에 연결하는 앵커 역할을 할 수도 있습니다. 진핵생물에서 발견되는 지질 고정의 세 가지 주요 유형은 - 프레닐 그룹, 지방 아실 그룹, 글리코실포스파티딜이노시톨 또는 GPI 그룹입니다. 프레닐 및 지방 아실 그룹은 막의 세포질 표면에서 앵커 역할을 하는 반면, GPI는 세포외 측면에서 단백질을 고정합니다.

Ras 단백질과 같은 대부분의 프레닐화된 단백질의 카르복시 말단에는 CaaX 모티프 또는 CaaX 상자가 포함되어 있습니다. 여기서 "C"는 시스테인을 나타내고, "a"는 지방족 아미노산을 나타내고, "X"는 기타 아미노를 나타냅니다. 산성 잔류물. "X" 위치에 존재하는 아미노산은 단백질에 대한 연결이 파르네실인지 아니면 게라닐게라닐 연결인지를 결정합니다. "X"가 알라닌, 세린, 메티오닌, 시스테인 또는 글루타민인 경우 파네실 전이효소는 CaaX 모티프를 인식하고 파네실을 단백질에 연결합니다. 반면, "X'"가 글루탐산 또는 류신인 경우, 게라닐 트랜스퍼라제 유형 I은 CaaX 모티프를 식별하고 이에 게라닐게라닐을 부착합니다. 프레닐화 후, 트리펩타이드 aaX는 특정 프로테아제에 의해 제거되고, 메틸트랜스퍼라제는 생성된 음전하를 띤 시스테인 잔기를 메틸화합니다. 메틸화는 시스테인에 존재하는 음전하를 제거하고 소수성을 만듭니다.

때로는 단백질을 막에 연결하기 위해 하나 이상의 지질 앵커가 사용됩니다. 예를 들어, 세포질 티로신 키나제는 미리스트산과 팔미트산의 도움으로 막에 고정됩니다. 그러나 GPI 고정 단백질은 일반적으로 안정화를 위해 또 다른 고정이 필요하지 않습니다. GPI의 한쪽 끝은 지질 이중층에 삽입될 수 있는 두 개의 지방 아실 그룹을 포함합니다. 대조적으로, 포스포에탄올아민은 다른 세포 기능과 관련된 표적 단백질에 부착됩니다.

원형질막에서 이중층을 형성하는 지질은 단백질을 원형질막에 묶는 앵커 역할도 할 수 있습니다. 지질 앵커의 세 가지 주요 유형 ...

Education

교육

JoVE Core

Cell Biology

세포생물학

Unit 1

제1단원

Membrane Structure and Components

막 구조 및 구성 성분

KEY TERMS AND CONCEPTS

주요 용어 및 개념

lipid anchors in membrane proteins

Lipid anchors help attach proteins to the plasma membrane. In eukaryotic cells, the main lipid anchors are prenyl groups, fatty acyl groups, and glycosylphosphatidylinositol, or GPI, groups. Prenyl and fatty acyl groups anchor proteins on the cytosolic side of the membrane. GPI anchors proteins on the extracellular side.

Prenylated proteins often have a CaaX motif at the carboxy terminus. In this sequence, C means cysteine, a means any aliphatic amino acid, and X means any other amino acid residue. The amino acid at the X position helps decide the type of linkage. If X is alanine, serine, methionine, cysteine, or glutamine, farnesyl transferase attaches a farnesyl group. If X is glutamic acid or leucine, geranylgeranyl transferase type I attaches a geranylgeranyl group.

After prenylation, specific proteases remove the aaX tripeptide. Then a methyltransferase methylates the cysteine that remains. This step removes the negative charge on the cysteine and makes it more hydrophobic. The change helps the protein stay associated with the membrane.

Some proteins use more than one lipid anchor. A cytoplasmic tyrosine kinase, for example, is anchored with both myristic acid and palmitic acid. GPI-anchored proteins usually do not need a second anchor for stability. The GPI group has two fatty acyl groups that insert into the lipid bilayer. Its other end contains phosphoethanolamine, which links to target proteins involved in different cell functions.

Lipid Anchors in Membrane Proteins

what are membranes?

Membrane Receptors and Cell Signals

The plasma membrane sets the outer boundary of a cell and helps control how the cell interacts with its environment. It lets some substances enter, keeps others out, and releases some materials in controlled amounts. The membrane also needs to stay flexible so cells such as red and white blood cells can change shape as they move through narrow capillaries. The membrane surface also carries markers that help cells recognize one another. This recognition is important during early development,...

membrane fluidity

How Cell Membranes Stay Flexible

Cell membranes stay flexible because of the fluid mosaic model. The plasma membrane is a mosaic of phospholipids, cholesterol, proteins, and carbohydrates. These parts are separate but loosely attached, so the membrane keeps a fluid character. The membrane is still fairly rigid, but it can flow and self-seal after a very fine needle passes through it. Phospholipid tails also affect membrane fluidity. Saturated fatty acids in phospholipids have straight tails because they are packed with...

fluid mosaic model

Fluid Mosaic Model of the Membrane

The fluid mosaic model explains the structure and function of the plasma membrane. Scientists first identified the plasma membrane in the 1890s, and by 1915 they had identified its main chemical parts: lipids and proteins. Early electron micrographs showed a railroad track pattern, which helped lead to the first widely accepted membrane model in 1935.

membrane lipids

Membrane Lipids in Cells and Tissues

Membrane lipids give biological membranes their structure and help set their properties. In mammalian cells, lipids make up about 50% of the membrane on average. The amount can be much lower in the inner mitochondrial membrane or much higher in the myelin sheath around nerve cells. Several phospholipids are common in mammalian membranes. These include phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and sphingomyelin. At physiological pH, phosphatidylserine carries a negative...

asymmetric lipid bilayer

Membrane Lipid Unevenness

Biological membranes have an uneven mix of lipids between the inner and outer layers. This membrane asymmetry gives each side a different chemical makeup and supports different cell functions. Evidence for this uneven layout came from treating an erythrocyte membrane with phospholipase. Phospholipase is an enzyme that breaks lipids into fatty acids and hydrophilic groups. It acted only on the outer layer, while the inner layer stayed intact. The treatment degraded about 80% of total membrane...

membrane asymmetry regulating transporters

membrane-asymmetry-regulating-transporters

Membrane Lipid Flipping and Transport

Membrane lipid flipping and transport help cells keep an uneven, or asymmetric, distribution of phospholipids across the membrane. This balance is controlled by flippase, floppase, and scramblase enzymes, which move lipids between the two membrane leaflets. Flippases move specific phospholipids from the outer leaflet to the inner leaflet. In eukaryotes, these enzymes are type-IV P-type ATPases, also called P4-ATPases. They are membrane pumps that use ATP and contain one transmembrane domain...

membrane carbohydrates

Membrane Sugars and Cell Identity

Membrane carbohydrates help give cells their surface identity and support plasma membrane function. The plasma membrane is a dynamic barrier made of lipids, proteins, and carbohydrates. These sugar chains have unique structural and chemical traits that help the membrane work properly for cell growth and survival. Membrane carbohydrates do not have a hydrophobic region, so they are found only on the outer surface of the cell. Sugar addition, or glycosylation, of proteins occurs in the lumens of...

membrane proteins

Facilitated Transport Across Cell Membranes

Facilitated transport uses membrane proteins to help materials cross the plasma membrane. These integral transmembrane proteins act as channels or carriers. They move selected substances through the membrane more easily than the lipid layer alone would allow. Channel proteins provide a hydrophilic, or water-friendly, path through the membrane. Their core forms a hydrated opening that lets solutes pass between the inside and outside fluids of the cell. This helps polar compounds avoid the...

lipids as anchors

Lipid anchors help attach proteins to the plasma membrane. In eukaryotic cells, the main lipid anchors are prenyl groups, fatty acyl groups, and glycosylphosphatidylinositol, or GPI, groups. Prenyl and fatty acyl groups anchor proteins on the cytosolic side of the membrane. GPI anchors proteins on the extracellular side. Prenylated proteins often have a CaaX motif at the carboxy terminus. In this sequence, C means cysteine, a means any aliphatic amino acid, and X means any other amino acid...

single-pass transmembrane proteins

How Membrane Proteins Span Cell Membranes

Membrane proteins help cells communicate, send signals, stick to other cells, and move molecules across the membrane. Integral membrane proteins are tightly linked to the cell membrane and carry out these jobs. Some integral membrane proteins sit only in one membrane layer. Fatty acid amide hydrolase is one example, and it is found on the cytoplasmic side of the membrane monolayer. Other integral membrane proteins are transmembrane proteins, which span across the membrane. These proteins have...

multi-pass transmembrane proteins and &#946;-barrels

multi-pass-transmembrane-proteins-and-barrels

Membrane-Spanning Helices and β-Barrels

Membrane-spanning proteins can cross the cell membrane more than once. Their transmembrane chain usually folds into either an alpha-helix or a beta-strand. Alpha-helix multi-pass proteins are common, while beta-strand proteins are found mainly in gram-negative bacteria, mitochondria, and chloroplasts. Some multi-pass alpha-helix proteins are G-protein-linked receptors, or GPCRs, and bacteriorhodopsin. GPCRs have seven transmembrane alpha-helices. Each receptor also has its own extracellular...

detergent purification of membrane proteins

detergent-purification-of-membrane-proteins

How Detergents Solubilize Membrane Proteins

Detergents help solubilize membrane proteins so they can be purified from the lipid bilayer. Their hydrophobic region can replace membrane phospholipids and keep integral membrane proteins in solution. A detergent works well only when its monomers reach the critical micelle concentration, or CMC. At that point, the molecules assemble into micelles, which are small clusters of detergent. Above the CMC, free detergent monomers stay in equilibrium with the micelles. The CMC varies with the...

protein diffusion in the membrane

How Membrane Proteins Move Side to Side

Membrane proteins can move across the cell surface by lateral diffusion, and they can also rotate in place. Scientists confirmed lateral movement with a cell fusion experiment. Mouse and human cells were fused to make hybrid cells. The membrane proteins on the two cells were tagged with red and green fluorescent markers. At first, each color stayed on its own side of the fused cell. After 40 minutes, the colors mixed across the whole cell surface, showing that the proteins had moved laterally. <br...

membrane domains

Lipid Rafts and Sperm Membrane Regions

Membrane domains organize specific lipids and proteins in defined parts of a cell membrane. This arrangement supports cell signaling, adhesion, and other important cellular processes. These domains can vary in size, composition, function, and how long they last. Some membrane domains are built from proteins. The membrane can contain distinct protein groups that carry out a cell’s specific functions. A clear example is the plasma membrane of a human sperm cell, which has different proteins in...

mechanisms of membrane domain formation

How Cell Membranes Form Domains

Cell membranes form domains when lipids and proteins gather into distinct regions. These regions, or membrane domains, are shaped by different physical properties that help some molecules stay together while others move apart. Some domains form through protein-protein interactions. Others depend on specific lipids, such as sphingolipids and sterols. Large proteins, including bacteriorhodopsin, can also cluster and create visible membrane domains. Membrane proteins can be held in place by...

mechanisms of membrane-bending

How Proteins Shape Cell Membranes

Cell membranes can bend into many shapes because they are flexible and made of a fluid mosaic. That bending can be temporary, as in vesicles, or long-lasting, as in microvilli. Cells control the size, place, and time of membrane curvature. Membrane bending can start inside the membrane itself or from proteins attaching to it. Changes in lipid makeup can create curvature, and proteins can help by making the membrane asymmetric or by clustering certain lipids. The shape of integral proteins also...

key terms and concepts

Learn how prenyl, fatty acyl, and GPI anchors attach proteins to the plasma membrane, including the CaaX motif and key enzyme steps.

Lipid Anchors in Membrane Proteins | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.3

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ATP Energy Storage and Release

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1. Engage in evidence-based argument to relate a cell's function to the structure, function, and diversity of its components. Examples: Muscle cells have a large number of mitochondria, which create energy for contraction in the form of ATP. Some plant cells have a large vacuole which is used for storage and transport of excess nutrients in changing environments.

9-12.B.1.1

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Pre-mRNA Processing: RNA Splicing

Chromatin Structure and RNA Splicing

Alternative RNA Splicing

Nuclear Export of mRNA

Transfer RNA Synthesis

Ribosomal RNA Synthesis

The Nucleolus

Additional Subnuclear Structures

Translation

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Initiation of Translation

Termination of Translation

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Nonsense-mediated mRNA Decay

The Eukaryotic Promoter Region

Molecular Chaperones and Protein Folding

Co-activators and Co-repressors

The Proteasome

Master Transcription Regulators

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Regulated mRNA Transport

Proteins: From Genes to Degradation

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Small interfering RNAs (siRNA)

Cis-regulatory Sequences

lncRNA - Long Non-coding RNAs

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Cooperative Binding of Transcription Regulators

Epigenetic Regulation

Epigenetic changes alter the physical structure of the DNA without changing the genetic sequence and often regulate whether genes are turned on or off. ...

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9-12.B.1.2

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9-12.B.1.2.a

Lipid Anchors in Membrane Proteins

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